Column-current multiplexing driver circuit for high density proms

摘要

Current switches are used to control current into the columns during READ operations of a PROM. The circuit provides one such switch for each of the columns of the PROM and makes possible the use of a single current source which is connected to each of the switches but supplies current only to the column of the PROM that is currently selected for reading. A high voltage pre-bias is applied to the collectors of the NPN transistors used as current switches such that turn-on speed is improved because the collector parasitic capacitances are pre-charged to near the supply potential.